A population of patients with proliferative sickle cell retinopathy (sea-fans) with hemoglobin SS, SC, or S-Thalassemia will be recruited at the University of Illinois and the University Hospital of the West Indies. Two hundred eyes with documented sea-fans will be randomized into treatment or nontreatment groups. The treatment group will receive either argon laser (University of Illinois) or xenon arc photocoagulation (Kingston) to obliterate all neovascular tissue. The nontreated eyes will serve as a control group. Eyes will be followed every 3 to 4 months for 2 to 4 years with documentation of the incidence of vitreous hemorrhage, retinal detachment, and visual loss. This study should demonstrate the risk/benefit ratio of photocoagulation in preventing major complications of proliferative sickle retinopathy.